The invention relates to a power wrench comprising a housing with a forwardly extending tubular neck portion, a rotation motor, an output shaft extending coaxially through the neck portion and adapted to be connected to a screw joint, and a torque reaction bar supported on the neck portion via a splines coupling, and a nut engaging a threaded front section of the neck portion for axially clamping the reaction bar to the housing.
In a power wrench of this type the torque reaction bar is supported on the wrench housing via splines coupling which enables mounting of the torque reaction bar in a number of alternative angular positions relative to the housing. In each position the torque reaction bar is locked against rotational movements relative to the housing, but a nut is employed to apply an axial clamping force on the reaction bar against the wrench housing or at least prevent the reaction bar from moving relative to the wrench housing.
It is important, however, that the torque reaction bar is maintained in a proper torque transferring engagement with a stationary object during screw joint tightening operations, because if the reaction bar suddenly should loose that engagement the reaction bar and perhaps the entire power wrench might be thrown off the screw joint in an uncontrolled way, which would be very dangerous for the operator, and human injuries and damage to equipment and the object being worked may be caused. Therefore, it is important that the reaction bar is at least rigidly secured to the power wrench housing to minimize the risks for accidents.
In a power wrench of the above described type where a clamping nut is used for maintaining the reaction bar secured to the wrench housing it is important to provide a lock means to prevent the nut from loosen unintentionally. Accordingly, it is an object of the invention to increase the safety properties of a power wrench by providing the clamping nut assembly with a lock means for avoiding unintentional loosening of the nut assembly.
It is another object of the invention to provide a power wrench with a reaction bar clamping nut assembly having a manually operable lock means conveniently shiftable between a lock position and a release position.
It is a further object of the invention to provide a power wrench with a torque reaction bar supported on a front end splines coupling and clamped to the wrench housing by a nut assembly, wherein the nut assembly comprises a lock means that does not require any special design features on the power wrench housing.
Further objects and advantages of the invention will appear from the following specification and claims.
A preferred embodiment of the invention is described below in detail with reference to the accompanying drawings.